The present invention relates to a spraying apparatus for unhardened concrete, etc. and more particularly, to an apparatus provided with means for mixing quick-set additives for rapid bonding agents with the unhardened concrete.
Up to the present, there have been proposed a number of process-methods each comprising the steps of mixing quick-set additive with the unhardened concrete and subsequently spraying the mixture. However, it is well known in the art that the effective accomplishment of the step of uniformly mixing the quick-set additive with the unhardened concrete by a simple procedure is extremely difficult, thus, most conventional process-methods of homogenizing the density throughout a substance produce unsatisfactory results when applied to an apparatus for mixing quick-set additives with unhardened concrete.
More specifically, according to a typical apparatus for feeding the quick-set additive by constant amount, there has been conventionally provided a screw conveyer in the lower portion of a particulate quick-set additive container so that the particulate matter located in the lower portion inside the container may be carried to a predetermined place outside the container. However, the particulate matter which lies relatively low inside the container, i.e., the particulate matter stored in the lower layer inside the container, is naturally compressed by the weight of the particulate matter lying relatively high inside the container, which results in the portion lying low inside the container becoming higher in density than that lying high. Particularly, when the container is substantially filled with the particulate matter, the particulate matter in the lower layer becomes greater in density through being compressed by the weight of a large amount of particulate matter in the upper layer. Alternatively, when the stored particulate matter is reduced in amount, due to the discharging operation of the particulate matter, the weight of the particulate matter located in the upper layer is gradually reduced, thus resulting in a gradual decrease in the density of the particulate matter in the lower layer. Since the particulate matter in the lower layer to be carried by the screw conveyer is varied in density depending upon the stored amount of particulate matter inside the container as described above, the density is varied if the particulate matter of the apparently constant amount is carried by the screw conveyer, whereby it has been quite difficult to discharge the particulate matter of the constant quantity and further, it cannot be expected that the predetermined quantity of the quick-set additive is mixed into the unhardened concrete.